Arm for a chair



FIG. 1 is a side view of an arm for a chair showing my new design; thebroken lines shown in the drawings are for illustrative purposes onlyand form no part of the claimed design;

FIG. 2 is a front view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom perspective view thereof; and,

FIG. 5 is a top perspective view thereof.

The ornamental design for the arm for a chair, as shown and described.